Method of growing quartz single crystals



Feb. 2, 1960 JAFFE EI'AL 2,923,605

METHOD OF GROWING QUARTZ SINGLE CRYSTALS Filed Sept. 29, 1954 3Sheets-Sheet 1 INVENTORS HANS JAFFE THADDEUS J-TURO BINSKI ATT Feb. 2,19-60 H. JAFFE ET L 2,923,605

METHOD OF GROWING QUARTZ SINGLE CRYSTALS Filed Sepc 29. 1954 3Sheets-$heet 2 INVENTORS HANS JAFFE THADDEUS J. TUROBI'NSKI Q MXT'KWFeb. 2, 1960 JAFFE EI'AL METHOD OF GROWING QUARTZ SINGLE CRYSTALS FiledSept. 29, 1954- 3 Sheets-Sheet 3 5 IN VEN TOR-S HANS JAFFE THADDEUS J.TUROBINSKI W ATTO NEY METHOD OF GROWING QUARTZ SINGLE CRYSTALS a.

Hans Jalfe and Thaddeus J. Turobinski, Cleveland Heights, Ohio,assignors to Clevite Corporation, Cleveland, Ohio, a corporationofOhiolg i Application September 29,, 1954, Serial No. 459,052 3 Claims.(Cl. 23-301 This invention relates to the growing of artificial quartzsingle crystals.

Crystal plates of quartz have for many years been used extensively asfrequency determining elements in radio frequency oscillators,electrical .filters, and the like. In consequence of the continuingdemand for such crystal plates, considerable advances have been made inrecent years in the synthesis of large single crystals of quartz fromwhich such crystal plates may be fabricated. Illustrative of suchadvances are the apparatus and method described and claimed in US.Letters Patent 2,675,303 to Andrew R. Sobek and Danforth R. Hale,assigned to the same assignee as the present invention. In accordancewith the general procedure of this patent, successful synthesis ofsingle crystals of quartz has been obtained by exposing a quartz crystalseed under conditions of elevated temperature and pressure to an aqueousmedium containing substantial quantities of an alkali metal carbonate,such as sodium carbonate or sodium bicarbonate. The aqueous medium ismaintained in contact with a supply material of crystalline quartz andcrystal growth takes place by the transfer of'silica from the supplymaterial to the quartz seed. Other methods have also been'employed withsuccess in which the quartz seed is exposed to other suitablepredetermined chemical and physical environments which promotecrystalline growth on the seed to produce a quartz crystal bar fromwhich crystal plates may be fabricated.

Experience in the synthesis of single crystals of quartz in the variouschemical and physical environments in which successful growth has beenachieved has demonstrated that quartz is one of the types of crystalswhich usually grow elongated in one direction, in the case of quartz,along the Z crystal axis. The fully grown quartz crystal, eithersynthetic or natural, between its ends tends to be in the shape of anelongated prism bounded by aset of six faces, known as the primary prismfaces, which the best results in growing quartz crystals have beenobtained heretofore by the use of quartz seed plates having their majoropposite faces extending parallel to a minor rhombohedral crystal face.in the use of such seed plates is the rapid development of the majorrhombohedral faces on crystals grown from seed plates of this type,which cause the tapered shape of the crystal at either end and whichdecrease the total crystal growth rate, the end result being that muchof the grown crystal is not usable for the. production of oscillatorplates and the like. i

In the present invention a significant improvement is obtained in theyield of quartz material usable for piezoelectric plates, both withrespect to the crystal seed weight and with respect to the time of therun, as well as with respect to the available autoclave space forgrowing such crystals.

In accordance with the present invention, the limita whose major facesare inclined at substantial angles to extend in the direction of naturalelongation of the crys-,

tal. At either end the crystal is terminated primarily. by threeintersecting faces, known as the major rhombohedral faces, which producetapered end caps on the crystal. If a quartz crystal seed body of anydesired size and shape is permitted. to grow indefinitely, it willeventually develop into a crystal, bounded at the sides by the primaryprism faces and at either end by the major rhombohedral faces. Little orno crystal growth takes place on these faces after they have formedfully in the chemical and physical environments used successfully ingrowing quartz crystals.

One of the most important aspects of quartz synthesis is to obtain themaximum yield, i.e., the greatest amount of material usable for crystalPlates, from a given plant in a given time. Heretofore, it has beennecessary to employ relatively large quartz seed plates and the ratio ofgrown crystal weight to seed weight has not been as high as might bedesired. Furthermore, runs of relatively long duration have beenrequired and the available space in the. autoclave in which the crystalsare grown is not used as efiiciently as might be desired.- In practice,

all of the primary prism faces, as well as at substantial anglesto allof the major rhombohedral faces. Preferably, the length of the seed bodyand the period of crystal growth are so chosen that the total crystalgrowth in any direction on the seed is considerably less than theoriginal seed length. Because of these factors, the major rhombohedralfaces and the primary prism faces develop only to a moderate extent inthe growing period involved and do not unduly detract from the rate ofcrystal growth during this period. In addition, the present inventiontakes advantage of the inherent characteristic of quartz, in thepredetermined chemical and physical environments in whichquartz crystalgrowth has been carried on success: fully, riot to grow to anysignificant extent outward from its primaryprism faces by using anelongated narrow quartz seed body whose length essentially determines.the cross-sectional size to which the quartz crystal may grow and whoseorientation with respect to the crystallographic axes determines theshape to which the crystal may grow.

Preferablyfln the process ofthe present invention there elongated narrowmajor facesextending perpendicular to a crystallographic X-axis and tothe crystallographic Z- axis, although different cross-sectional shapesmight be used without departing from the spirit and scope of the presentinvention.

Accordingly, it is an object of the present invention to provide a novelmethod of growing single crystals of quartz which results in an improvedyield of usable crystal material with respect to the crystal seedmaterial required. l

Another object of this invention is to provide a novel method of growingsingle crystals of quartz which results in an improved yield of usablecrystal material with respect to the available autoclave capacity.

It is also an object of this invention to provide a novel method of,growing single crystals of quartz which results in a greater amount ofusable crystal material per unit of run time.

formation of the major rhombohedral crystal faces is less serious thanin the previous methods of quartz synthesis. Anotherobject of thisinvention is to provide a. novel However, a limiting factor 3 method ofgrowing a quartz single crystal which employs a lighter, thinner seedbody than required heretofore.

Other and further objects and advantages of the present invention willbe apparent from the following description of the preferred embodimentthereof, disclosed in detail in the following description referring to.the accompanying drawings.

4 In the followingdiscussion the standards adopted in the Standards onPiezoelectric Crystals (1949) of the Institute of Radio Engineers, setforth in the Proceedings of the I.R.E., vol. 37, pp. 1378-1395, arefollowed.

In the drawings: 1 I Figure l is a perspective view showing an idealizedfull grown large natural single crystal of quartz of the left-handedvariety and showing the orientation of the present quartz seed withrespect thereto;

Figure 2 is a transverse cross-section through .the middle of thecrystal of Fig. l and showing the orientation of thepresent quartz seed;,1

Figure 3 is an enlarged perspective view of a quartz crystal bar grownin accordance with the present invention;

Figure 4 is a top view, on a reduced scale, of the quartz crystal bar ofFig. 3: and I a Figure Sis a perspective view of the Fig. 3 crystal (ona smaller scale) with the tapered ends of the crystal removed andshowing the manner in which oscillator plates may be cut from thecrystal.

Referring to Fig. 1, there is shown an idealized natura crystal ofleft-handed quartz. As is well understood, this crystal is elongated inthe direction of the crystallographic Z-axis. At its middle the crystalis bounded by the six primary prism faces 11-16 characterized incrystallography by their Miller index {10T0}. These primary prism facesextend parallel to the crystallographic Z-axis, which is the directionof natural elongation of quartz. Each of these prism faces isintersected by a pair of neighboring primary prism faces, each inclinedat 60 thereto. At one end, in the direction of the crystallographicZ-axis, there are three intersecting major rhombohedral faces,identified by the reference numerals 17, 18 and 19 in Fig. l. The Millerindex for these major rhombohedral faces, as well as for theircounterparts 17', 18' and 19' at the opposite end of the crystal, is{1011}. Minor rhombohedral faces 20, 21, 22 and 20, 21', 22' of Millerindex {0111} are lo cated between the major rhombohedral faces. Fig. 1shows certain additional faces, known as the trigonal bipyramid andtrigonal trapezohedro-n faces, which sometimes occur in natural quartzcrystals but which are not important for an understanding of the presentinvention.

As shown in Fig. 1, the elongated crystal seed 40 employed in thepresent process has its length extending in a plane perpendicular to thecrystallographic Z-axis (which is the direction of elongation of thecrystal) and the crystal seed is elongated in the direction of acrystallographic Y-axis (perpendicular to a pair of parallel oppositeprimary prism faces, such as 13 and 16) and small in either directionperpendicular to the Y axis.

Since the length of the crystal seed extends in the direction of the Ycrystallographic axis, the seed is termed a Y-bar seed. As shown in Fig.2, the long dimension of the crystal seed 4% extends at 30 to the acrystal axis, at 30 to the a crystal axis, and at 90 to the a crystalaxis, these axes being crystallographically equivalent X axes. It willbe evident that with any other orientation of the crystal seedperpendicular to the Z crystal axis, the length of the crystal seedwould extend at an angle less than 30 with respect to a pair of theprism faces. -Accordingly, it may be stated that with theillustratedorientation of the crystal seed the seed lengthextends atangles to the primary prism faces inch )that the smallest of theseangles is a maximum The elongated quartz crystal seed 40. of thisorientation is cut from the mother crystal and is exposed to apredetermined chemical and physical environment which promotes crystalgrowth on the seed by the deposition of quartz from a transfer medium inwhich supersaturation of quartz is maintained to cause crystallinegrowth on the seed. Preferably, thetransfer medium is an alkalineaqueous solution in contact with a supply of silica, preferablycrystalline quartz, and the quartz seed is exposed to this solutionunder conditions of elevated temperature and pressure "which maintainsupersaturation of quartz around *the' seed to cause crystal growth onthe seed. For example, the particular physical and chemical conditionsdescribed in the above-mentioned Patent 2,675,303 might be employed. Theseed is supported by a suitable-holder arrangement (Fig. 3) engaging theseed at or near its opposite ends in the Y -axis direction andpermitting unconfined crystal growth on the seed in the directions ofthe crystallographic X- and Z-axes (perpendicular to the seed length).

From Figs. 14 it will be noted that the quartz seed 40 has opposite endfaces 13a and 16a which were part of the prism faces 13 and 16 on themother crystal. These end faces on the seed form substantially thecomnete primary prism faces of one pair on the crystal b r grown fromthe seed. In one practical embodiment the seed mav'be 6 inches long (inthe Y-axis direction) and 0.15 inch squarein cross-section (parallel tothe X- nd Z-axes, respectively).

Due to the inherent g owth habit of quartz in its nutrient medium, veryrapid growth will take place in the direc ion of the crystallographicZ-axis. This growth will p oceed substantially equally on opposite sidesof the seed in the Z'axis direction. We havefound that u te rapid rowthwi l take place also in the direction o the crvstallographic X-axis (thea axis, perpendicular to the length of the seed). However, this growthoccurs at a rateabout twice as fast on one side of the crvstal seed inthe X axis direction as on the other side. Rapid growth (but less thanthe growth rate in the Z- and X-ax s direc ions) takes place on theminor rhombohedral faces. Slow growth takes place on the maiorrhombohedral faces. Finally, no significant grnwth occurs on the primaryprism faces.

Due to this growth habit. the crystal bar increases rapid v in the Zaxis direction on opposite'sides of the rtz seed. producing the oppositefaces Z and Z (Fig. 3), which extend perpendicular to the Z axis. Also.the growing crystal bar tends to increase in size rapidl in the Xaxisdirection, producing the opposite f ces X and X Which extendperpendicular to the X axis. i

As a result. of the rapid growth in the X and Z directions the maiorrhombohedral faces become larger as the crvstal growth proceeds, as dothe two pairs of'primary prism faces not present on the seed 40.

At the ri ht end of the crvstal bar in Fig. 3 the intersecting maiorrhombohedral faces 17a and 19a are both relatively large. These maiorrhombohedral faces correspond to the maior rhombohed al faces '17 and 19on the mother quartz (Figure 1). The minor rhombohedral face(corresponding to the minor rhombohedral face 21, on the Fig. 1 motherquartz) which would be expected to appear between the maior rhombohedralfaces 17a and 19a and the primary prism face 16a (at the end of thecrvstal seed) has disappeared because of the rapidity with which crystalgrowth has occurred on it. In like manner, at the opposite end of theseed the crystal bar has developed relatively large maior rhombohedralfaces 17'a and 19'a, corresponding to the major rhombohedral faces 17and 19' on the mother quartz of Fig. 1. The minor rhombohedral facewhich would be expected to appear between these major rhombohedral faces17'a and 19'a and the primary prism face 13a (at the left end of thecrystal growth on it.

At the -right end ofthe crystal bar-i n Fig. 3,. the major rhombohedralface 18%, which corresponds to the; m i rhombohedral face 18 on themother crystal-40f; Fig. 1,, is considerably smallen in size thantheother: 11135.0 rhombohedral faces 17a and 19a atthis, endqofithe;crystal on the opposite side of the crystalainrthe; Z-axis; direction.The minor rhombohedral faces 20'aand1 21 a correspond ing to the minorrhombohedralfaces, 20;; and 21;; on the mother quartz of- Fig. 1, borderon. the majonrhoniho hedral face 18fa at opposite, sides thereof;

Similarly, atlthe left end of the Fig, ,3. crystal bar the majorrhombohedral face 18a, whicmcorresponds, to, they major rhombohedralface 18;,onthe Fig. l mother; crystal, is smallen than the majorrhombohedral faces. 1 71a and;

19'a at this end of the crystal bar on the opposite, side:

of the crystal in; the, Z -axis; direction; The minor rhombohedral faces20a and 21a, corresponding to the minor, rhombohedral faces 20; and 21on the mother quartz of Fig. 1, border on the major rhombnhedral face18non opposite sides thereof.

At the right end of the crystal bar in Fig. 3, :the; incomplete primaryprism face a extends awaylfrom the end face 16a of the crystal seed(which is; also a primary prism face) at an inclination of 60- theretm.Similarly, at the opposite end; of; the crystal seed the linw. completeprimary prism; face 14a extends (toward the; front in Fig. 3) away fromthe primary, prism end face, 13a of the crystal seed atan, inclinationof 6,0? thereto The primary prism faces 15a and 14a correspond to the;primary prism faces 15 and 14, on; the mother quartz of Fig. 1. Theseprimary prisrnfaceslSw and 14a eonvergea toward each other and wouldintersect; ultimately if-full; growth of the crystal bar were permitted.

At the right end of the back side ofFig. 3 crystal bar, the incompleteprism face 11a; extends away. from theprimary prism end faee;lfic on thecrystalseed 4llat an inclination. of 60 to thelatter face. A ttheopposite end; of the crystal seed theincomplete primary prismface 12aextends away from-the primaryprism end face 13a. onthe crystal seed ataninclination of 60 to thelatter face. These incomplete primary prism.faces 11a and 12a correspond to theprimary prism faces 11 and 12 on. themother quartz of Fig. 1. The primary prism faces 11a and 12aconyergetoward each other'andwouldintersect ultimately if the crystalbar were permitted to grow fully. It will be noted. that the primaryprism faces 11a and 12a on the back; side of the crystalbar in Fig. 3are more fully developed; than, the primary, faces 15a and 14a at thefront side because of the more rapid crystal growth in the X-axisdirectionon the back side of the crystal seed 4.0.in Fig. 3.

While the occurrence of crystallographic faces (labelled X and X in Fig.3) perpendicular to the X-axis in a grown quartzcrys tal is believed tobe novel and a consequence of the practice of our invention, adifference in growth rate at the opposite ends of. such XrflXiS is inaccordance with the well-known polar nature of this axis in quartz. Wehave found that upon compression in the direction of an X-axis positivecharge is developed. on the fast-growing end. This finding is ofpractical value as it enables quartz crystal seeds to be spaced andoriented in an autoclave so as to provide optimum usage ofgthe availablespace. Correlation between etch figures appearing on a face cutperpendicular to an X-axis of quartz and the electric polarity are wellknown. For the pur pose oforienting our quartz seed, etch figures cantherefore also be utilized: On the side of fast growth, the etch patternproduces a characteristic parallelogram when a pin point light source isviewed through the crystal seed: bar. From. knowledge, of thepolaritynofj the X-axis, and the arrangement of major and milolyrhornheherlral faces around this axis, the handedness of the crystalis determined. Thus, the crystal of Figure 3 is found to be lefthanded,and the well-developed front face X on the slow growing end of theX-axis has the index {E}.

If, the: crystal b'ar were permit-ted to grow fully, sci that theprimary prism faces 15a and 14a would intersect and the primary prismfaces 11a and, 12a would intersect, asindicated in dotted lines in Fig.4, then the fully developed prism faces 16a, 15a, 14a, 13a, 12a and11a,would lform a closed hexagonal prism.

It is important to note that the end faces 16a and 13a on the crystalseed do not change in size in the X direction as the crystal growthproceeds, since practically no crystalline growth takes place on thesefaces and the adjacent prism faces 15a, 11a, and 14a, 12a, respectively,because they are primary prism faces. Thus, since the directions inwhich the incomplete prism faces 15a, 11a, 14a and 12a,extend away fromthe primary prism end faces 16a and 13a on the seed are fixed], the sizeof the crystal bar in the X-axis direction is determined essentially bythe length of the crystal seeds. Accordingly, it may be considered thatcrystal growth in the X-axis. direction is essentially a filling out ofthe crystal bar to the cross-sectional size predetermined by the lengthand the crystallographic orientation of the Y-bar seed.

The major rhombohedral faces 17a and 19a at the right end of the crystalbar in Fig. 3 and the major rhombohedral faces 17'a. and l9a at the leftend of this crystal bar impose tapers on the ends of the crystal bar,limiting the growth of usable crystal material in the Z-axis direction.

In order to minimize: the waste of crystal material due to the tapers inthe Z-axis direction imposed by the major rhombohedral faces and thetapers in the X-axis direction imposed by theprimary prism faces whichextend away from the ends ofthe original crystal seed, the crystalpreferably should, be removed from the nutrient medium long before thecrystal has grown fully. The crystal growth should be terminated beforethe crystal has grown inany direction greater than. the length of theoriginal seed. In practice, with a seed having, a length of 6, inches,inHthe Y-axis direction, it is desirable to pick the crystal bar afterits total growth in the Z-axis direction] (its direction of most rapidgrowth) is of the order of A or less of the seed length. The resultant,partially grown crystal would have a shape approximately that indicatedin perspective in Fig. 3 andin full lines in Fig. 4.

By trimming oif the tapered, ends of this. crystal as by cuts along theplanes c c and d d in Fig. 4, there is. produced a block of quartz (Fig.5) of generally rectangular cross-section, except for minor tapers atcertain of its end corners. This block of crystal material would beabout 4 inches long in the Y-axis direction, assuming that the originalY bar seed was 6 inches long. Several oscillator plate blanks 41 of anextensively used type, known as the AT cut, may be cut from this crystalblock by cutting along spaced, parallel planes disposed at about 35 tothe crystallographic Z-axis, as indicated in Fig. 5. With a block of thesize specified above, a series of oscillator plate blanks may be cutfrom the top half of the crystal block shown in Fig. 5 and a series ofoscillator plate blanks also may be cut from the bottom half of thiscrystal block.

With the foregoing arrangement the yield of the crystal material usablefor piezoelectric plates, both with respect to the time of the run andwith respect to the amount of seed material required, is significantlyincreased. Due to the small weight of the present crystal seeds andavoidance of much of the unproductive tapered growth which occurs at thefinal phase of the development of a full grown quartzcrystal, a yield of0scillator plate blanks of the order of three or more times thatproduced by present techniques may be expected, both with respect to theweight of seed material. required and with respect to the availableautoclave capacity.

Where a crystal is grown in accordance with the present method for thepurpose of producing additional Y- bar quartz seeds, rather thanoscillator plate blanks, then 7 it will be preferable to let the crystalgrow more fully than the crystal illustrated in Fig. 3.

While in the foregoing description and in the accompanying drawingsthere has been disclosed a particular preferred embodiment of thepresent invention, it is to be understood that various modifications,omissions and refinements which depart from the-disclosed embodiment maybe adopted without departing from the spirit and scope of thisinvention. For example, the crystal seed might have its length lying ina plane transverse to the Z crystal axis, but not exactly perpendicularthereto. Thus, the length of the crystal seed might extend at an angleas small-as 55 to the crystallographic Z-axis, although this will resultin a reduced yield and is not considered desirable. Also, the length ofthe crystal seed might not extend precisely at angles of 90, 30 and 30to the respective -aaxes of the crystal (i.e., in the direction of thecrystallographic Z-axis). The basic advantages of the present inventionwould be substantially accomplished even though such minor deviationsfrom the specific preferred embodiment disclosed above are adopted.Accordingly, such variations are considered to fall within the spiritand scope of the present invention.

7 We claim:

1. A method of growing a quartz single crystal in a predeterminedchemical and physical environment which promotes quartz crystal growthand in which environment the quartz crystal tends to have crystal growthon its primary prism faces inhibited, which method comprises the stepsof: providing an elongated quartz crystal seed bar having its lengthextending substantially perpendicular to a crystallographic X-axis andat an angle greater than 55 to the Z axis of the crystal; and exposingsaid seed bar to a fluid growing medium which provides supersaturationof quartz in the neighborhood of the seed body to cause crystal growthon the seed body.

2. A method of growing a quartz single crystal by the deposition ofquartz from a growing medium onto a quartz seed which comprises thesteps of: providing an elongated quartz crystal seed bar having itslength extending substantially perpendicular to a crystallographicX-axis and substantially perpendicular to the Z-axis of the crystal,saidseed bar being small in cross-sectional dimensions perpendicular toits length; and exposing said seed body to a fluid growing medium whichprovides supersaturation of quartz in the neighborhood of the seed bodyto cause'crystal growth on the seed body.

3. A method of growing a quartz single crystal in a predeterminedchemical and physical environment which promotes quartz crystal growthand in which the quartz crystal tends to have substantially nosignificant growth on its primary prism faces, which method comprisesthe steps of: providing an elongated quartz crystal seed bar having itslength extending in the direction of a Y crystal axis and small incross-sectional dimensions perpendicular to its length; and exposingsaid seed bar to said chemical and physical environment to cause crystalgrowth on the seed bar in the direction of the crystallographic Z- axis,as well as perpendicular to said Z-axis and perpendicular to saidY-axis.

4. A method of growing a quartz single crystal by the deposition ofquartz from a transfer medium onto a quartz crystal seed which comprisesthe steps of: providing an elongated quartz crystal seed bar having itslength extending substantially perpendicular to a crystallographicX-axis and at an angle greater than 55 to the crystallographic Z-axis;and exposing said seed to a fluid transfer medium in which a conditionof supersaturation of quartz is maintained adjacent the seed to promotecrystal growth on the seed.

5. A method of growing a quartz single crystal by the deposition ofquartz from an aqueous transfer medium onto a quartz seed whichcomprises the steps of: providing an elongatedquartzjcrystalseed barhaving its length extendingsubstantially perpendicular to thecrystallographic Z-axis andsubstantially perpendicular to acrystallographic X-axis; supporting said seed bar at its ends to 1permit unconfined crystal growth on the seed bar bewhich providesupersaturation of quartz in said medium around the seed bar to promotecrystal growth on the seed bar.

6. A method of growing a quartz single crystal by the deposition ofquartz from an aqueous solution onto a quartz crystal seed whichcomprises the steps of: providing an elongated quartz crystal seed barhaving its length extending substantially perpendicular to acrystallographic X-axis and at an angle greater than 55 to thecrystallographic Z-axis; and exposing said seed bar, while supported forunconfined crystal growth on the seed body between its ends, to analkaline aqueous solution in contact with a supply of crystalline quartzand under conditions of elevated temperature and pressure whichestablish supersaturation of quartz in the solution adjacent the seedbar to cause crystal growth on the seed bar.

7. A method of growing a quartz single crystal by the viding anelongated quartz crystal seed bar .having its length extendingsubstantially parallel to a crystallographic Y-axis and small incross-sectional dimensions transverse to its length; and exposingsaidseed bar,'while supported at its ends to permit unconfined crystalgrowth on the seed bar in the directions of the crystallographic X- andZ-axes, under conditions of elevated temperature and pressure to analkaline aqueous solution in contact with a supply of crystalline quartzand in which solution supersaturation .of quartz is maintained topromote crystal growth on the seed bar.

8. A method of growing a quartz single crystal by the transfer of quartzfrom an aqueous growing solution onto a crystal seed which comprises thesteps of: providing an elongated quartz crystal seed bar having itslength extending substantially parallel to a crystallographic Y-axis;and exposing said seed bar under growing conditions at elevatedtemperature and pressure to an aqueous solution in contact with a supplyof silica to effect the transfer of quartz onto the seed bar. I

References Cited in the file of this patent UNITED STATES PATENTS Re.19,697 Kjellgren Sept. 10, 1935 1,906,758 Kjellgren May'2, 19332,309,467 Mason Jan. 26, 1943 2,468,761 Kjellgren May 3, 1949 2,508,208Wooster May 16, 1950 2,638,408 Friedman et a1. May 12, 1953 2,674,520Sobek Apr. 6, 1954 2,675,303 Sobek et al. Apr. 13, 1954 OTHER REFERENCESBeane et al.: The Marconi Review, No. 111, vol. XVI, 4th Quarter 1953,pages 141 to 168, Figures 1 and 17.

Thomas et al.: Faraday Society, Discussion No. 5, 1949, pages 343344. I

1. A METHOD OF GROWING A QUARTZ SINGLE CRYSTAL IN A PREDETERMINEDCHEMICAL AND PHYSICAL ENVIRONMENT WHICH PROMOTES QUARTZ CRYSTAL GROWTHAND IN WHICH ENVIRONMENT THE QUARTZ CRYSTAL TENDS TO HAVE CYRSTAL GROWTHON ITS PRIMARY PRISM FACES INHIBITED, WHICH METHOD COMPRISES THE STEPSOF: PROVIDING AN ELONGATED QUARTZ CRYSTAL SEED BAR HAVING ITS LENGTHEXTENDING SUBSTANTIALLY PERPENDICULAR TO A CRYSTALLOGRAPHIC X-AXIS ANDAT AN ANGLE GREATER THAN 55* TO THE Z AXIS OF THE CRYSTAL, AND EXPOSINGSAID SEED BAR TO A FLUID GROWING MEDIUM WHICH PROVIDES SUPERSATURATIONOF QUARTZ IN THE NEIGHBORHOOD OF THE SEED BODY TO CAUSE CRYSTAL GROWTHON THE SEED BODY.